a1 Department of Psychiatry and Neuropsychology, European Graduate School of Neuroscience, Maastricht University, The Netherlands, and Division of Psychological Medicine, Institute of Psychiatry, London, UK
Summary Aims - Schizophrenia is a severe mental illness that affects 1% of the population. The diagnosis is made according to current diagnostic systems of DSM-1V (American Psychiatric Association, 1994) and ICD-10 (World Health Organisation, 1992), on the basis of characteristic ‘positive’ and ‘negative’ symptoms. The traditional model assumes a categorical view of the schizophrenia syndrome and its core symptoms, in which differences between psychotic symptoms and their normal counterparts are considered to be qualitative. An alternative, dimensional approach assumes that schizophrenia is not a discrete illness entity, but that psychotic symptoms differ in quantitative ways from normal experiences and behaviours. This paper reviews evidence for the continuity of psychotic symptoms with normal experiences, focusing on the symptoms of hallucinations and delusions. Methods - A qualitative review of the relevant literature. Results - The literature suggests that although current epidemiological approaches yield substantial evidence for a continuum view, it is rarely interpreted as such. Conclusions - The traditional concept ofschizophrenia as a homogeneous disease entity has become outdated and is in dire need of a more valid and clinically useful successor.
Declaration of Interests Support has been received in the last two years from the Dutch Research Council, The Dutch Ministry of Health, Maastricht University, The Dutch Brain Society, ZON-MW, The Province of Limburg, The Council of Maastricht, Eli Lilly, Janssen-Cilag, Pfizer, Astra-Zeneca and Bristol Meyer Squibb. None of these funding sources represents a conflict of interest in relation to this article.
(Received November 08 2003)
(Accepted November 18 2003)
c1 Address for correspondence: Professor J. van Os, Department of Psychiatry and Neuropsychology, Section of Social Psychiatry and Psychiatric Epidemiology, PO Box 616 (DRT10), 6200 MD Maastricht (The Netherlands). Fax: 31-43-387.5444